GROWTH OF THE CORAL COLONY 81 



exfoliating plates, and then it may bear zooids on both surfaces 

 of the plates, or on the upper surface alone. In every case 

 where zooids are borne both above and below, there is the 

 same marked difference of structure between the two surfaces. 

 When the linear growing point grows uniformly upwards, 

 the resulting growth consists of a series of vertical plates ; 

 and when the growth takes this form, the structure of both 



Fic4. 20. 



m^ 



Vegetative Reproduction in Corals. 



Diagrammatic section to illustrate the mode of growth of Montipora : 

 the uppermost zooids are the most newly formed. 



sides of the plate is identical, and zooids grow from both 

 surfaces. 



A plate-like growth is formed by a uniform and con- 

 tinuous growing edge ; but the linear series of young growing 

 zooids may not maintain their continuity : the growing edge 

 may reach a certain size and then divide, and the resulting 

 growth consequently takes the form of a plate, cleft at its 

 edges, or of a branching form, all of whose branches are given 

 off in one plane. This is a highly characteristic form of 

 growth of one type of Montipora which is abundant in the 

 islands, and it grades very naturally into the plate-like growths 



